3 Mar 2011

G3XIZ copied on VLF (at last)

G3XIZ received on VLF
Overnight, Chris G3XIZ was transmitting a test carrier on 9.0909kHz using 80W into his normal inverted-L antenna used on 136 and 500kHz matched with a large VLF loading coil. Using Spectrum Lab software and 423uHz bandwidth FFT settings I managed to get quite good copy of his signal using my 80 sq metre loop and small FET preamp. Between 0300-0600 his signal was around 10dB S/N in this bandwidth. Distance between us is around 45km. Later I got this email from Chris:
"You've re-awakened my enthusiasm which I must confess was fading. You are absolutely correct -  I checked the transmitter about 02.30 and found that the aerial current had dropped off, maybe due to a change in loading coil inductance with temperature. I increased the drive and brought it back to the initial level of 0.18 A. You and I seem to be at the extreme range with my current set up and if the new loading coil is more efficient we must try the experiment again. I am pleased that the OCXO seems to stable enough for our purposes. Once I've cured my off air standard of losing 'lock' I'll use that as the frequency source. My TX input power was 120 watts giving an output RF of about 80 watts. This should automatically be increased with the better loading coil."
UPDATE: Paul Nicholson in Todmorden Yorks has confirmed he received Chris at a distance of 218km, a new record for a UK VLF ham station.

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